1. Field of the Invention
The present invention relates to a semiconductor integrated circuit processed to be easily tested, and a method of testing the same.
2. Description of the Background Art
In conventional arts, a crystal oscillator, a ceramic oscillator, CR oscillator and the like has been used as a clock generator of an IC tester for testing a semiconductor integrated circuit (IC). Employing a clock just generated by the clock generator as a clock of the IC to be tested (DUT; Device Under Test), an operation test of the DUT has been performed.
A burn-in is one of the methods of operation test of the IC. In practicing a burn-in, in order to reject structural defects of the IC (e.g. defects of a gate oxide film in a MOS structure) in an early stage, stress should be applied to the IC under severer condition (higher temperature, higher voltage) than that in actual operation. The stress is several hundreds to several tens times as much as that in actual operation. There are two types of burn-ins, i.e., a static burn-in and a dynamic burn-in. In the static burn-in, the stress is applied to the IC without operation, while in the dynamic burn-in, the stress is applied to all of the internal elements of the circuit with the IC in operation. Following the burn-in, a normal functional test is given to the IC, thereby checking if the IC can normally operate, and further an acceleration test may be given thereto.
In recent, with refinement of process rule and enlargement in scale of incorporated circuit, the dynamic burn-in is becoming a leading mainstream. Since a purpose of the dynamic burn-in lies in performing the acceleration test, it is necessary to conduct the test under severer condition than that in actual operation. With speed up of an operating clock of an LSI, the clock generator of an IC driving device which conducts the dynamic burn-in is required to supply a clock higher than that in actual operation of the LSI.
In the conventional clock generator using the crystal oscillator and the like, however, it is so difficult to generate a high-frequency clock which is capable of answering the high-speed operation of the IC that the clock generator which can generate the high-frequency clock is highly priced.
Thus, since it is impossible to achieve the clock generator of the IC tester which is capable of answering the high-speed operation of the IC at a low cost, there arises a problem that the functional test or such a test as burn-in of the IC can not be performed by means of a relatively low-priced IC tester with the high-frequency clock which is capable of answering the high-speed operation of the IC.